Maintain HeadlessService on upgrade

[vepatel]

Proposed changes

• Updates createHeadlessService() to check if headless service from earlier installation exists, if yes then update the labels and ownerReferences (in case cm changes)

After upgrade:

1 main.go:1147] Headless service default/test-release-nginx-ingress-controller-replicaset-hl exists and needs update. Updating... 1 main.go:1084] Pod label updated: test-release-nginx-ingress-controller-6d887d4947-9hqzp 1 main.go:109] Event(v1.ObjectReference{Kind:"Pod", Namespace:"default", Name:"test-release-nginx-ingress-controller-6d887d4947-9hqzp", UID:"41b1f9e9-a38e-478e-a7db-91c0db341ce2", APIVersion:"v1", ResourceVersion:"1749129780125903017", FieldPath:""}): type: 'Normal' reason: 'UpdatePodLabel' Successfully added version labels, app.kubernetes.io/instance="test-release", app.kubernetes.io/name="nginx-ingress", pod-template-hash="6d887d4947", app.nginx.org/version="1.27.4-nginx-plus-r34-p1", app.kubernetes.io/version="hl-fix" 1 main.go:1152] Successfully updated headless service default/test-release-nginx-ingress-controller-replicaset-hl. 

replicaset selectors:

Name: test-release-nginx-ingress-controller-6d887d4947 Namespace: default Selector: app.kubernetes.io/instance=test-release,app.kubernetes.io/name=nginx-ingress,pod-template-hash=6d887d4947 

headless service selectors:

Name: test-release-nginx-ingress-controller-replicaset-hl Namespace: default Labels: <none> Annotations: cloud.google.com/neg: {"ingress":true} Selector: app.kubernetes.io/instance=test-release,app.kubernetes.io/name=nginx-ingress,pod-template-hash=6d887d4947 

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes
• I have updated necessary documentation
• I have rebased my branch onto main
• I will ensure my PR is targeting the main branch and pulling from my branch from my own fork

[codecov]

Codecov Report

Attention: Patch coverage is 89.18919% with 4 lines in your changes missing coverage. Please review.

Project coverage is 52.69%. Comparing base (f8d5420) to head (a702777).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
cmd/nginx-ingress/main.go	89.18%	3 Missing and 1 partial ⚠️

Additional details and impacted files

@@ Coverage Diff @@ ## main #7865 +/- ## ========================================== + Coverage 52.51% 52.69% +0.17%  ========================================== Files 90 90 Lines 21581 21598 +17 ========================================== + Hits 11334 11380 +46  + Misses 9776 9743 -33  - Partials 471 475 +4 

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